Volcanoes as emission sources of atmospheric mercury in the Mediterranean basin

Emissions from volcanoes, fumaroles and solfataras as well as contributions from widespread geological anomalies could represent an important source o f mercury released to the atmosphere in the Mediterranean basin. Volcanoes located in this area (Etna, Stromboli and Vulcano) are the most active in E urope; therefore, it is extremely important to know their mercury contribut ions to the regional atmospheric budget. Two main methods are used for the evaluation of volcanic mercury flux: a direct determination of the flux (by measuring in the plume) and an indirect one derived from the determination of the Hg/SO2 (or Hg/S) ratio value, as SO2 emissions are constantly monit ored by volcanologists. An attempt to estimate mercury flux from the Vulcan o volcano and to establish the Hg/S ratio value has been made along three f ield campaigns carried out in October 1998, in February and May 1999 sampli ng several fumaroles. Traditional sampling methods were used to collect bot h total Hg and S. The average Hg/S ratio value resulted to be 1.2 X 10(-7). From the Hg/S value we derived the Hg/SO2 value, and by assuming that all the volcanoes located in this area have the same Hg/SO2 ratio, mercury emis sions from Vulcano and Stromboli were estimated to be in the range 1.3-5.5 kg/year and 7.3-76.6 kg/year respectively, while for Etna mercury flux rang ed from 61.8 to 536.5 kg/year. Data reported in literature appear to be ove restimated (Fitzgerald WF. Mercury emission from volcanos. In: 4th Internat ional conference on mercury as a global pollutant, August 4-8 1996, Hamburg , Germany), volcanic mercury emission does not constitute the main natural source of the metal. (C) 2000 Elsevier Science B.V. All rights reserved.